©Societas Europaea Lepidopterologica; download unter http://www.biodiversitylibrary.org/ und www.zobodat.at Nota lepid. 11 (3) : 177-181 ; 31X1988 ISSN 0342-7536 On the distribution of Tarucus îheophrastus (Fabricius, 1793) (Papilionoidea, Lycaenidae) in Morocco. Arturo Baz Dept. de Biologia Animal, Universidad de Alcalâ de Henares, E-28871 Alcalâ de Henares. Madrid, Spain. Summary The distribution pattern of Tarucus îheophrastus in Morocco is discussed. Two areas of increased population density have been found, one in the south and one in the north. There appears to be a positive inverse correlation between population density and altitude. The optimum altitude was found to be between 400 and 800 m. Résumé Dans ce travail, on étudie le modèle de distribution de Tarucus îheophrastus au Maroc. La densité des peuplements est plus grande dans quelques régions de l'aire de distribution et diminue vers les limites de ces régions. La cause probable est un gradient d'élévation agissant comme facteur limitant. Introduction Tarucus îheophrastus (Fabricius, 1793) is essentially an eremic species that flies from Southern Spain and Morocco through the arid Sahel zone of Africa to South-western Arabia, Dhofar (Larsen, 1984) and Yemen (Balleto & Larsen, 1985). The records from India (see, however, Khatri, 1987) the Middle East and Egypt are probably due to misidentifications (see Benja- mins 1983, 1984 and Balleto & Larsen, 1985). In Morocco, the species is known from the north-eastern semi-arid zones (Higgins & Riley, 1980) with a few records from Marrakech and Oukaime- den in the High Atlas Mountains (Hall, 1986) and from Taroudant, Ait-Baha and Ait-Melloul on the southern slopes of these mountains (De Prtns et al, 1984 ; see also Rungs, 1981). The larvae feed on bushes and trees of Zizyphus sp., eating the leaves (one side only). In nature, the larvae are tended by ants in a symbiotic relation- ship, but in captivity they will develop satisfactorily without the attention of ants (Larsen & Larsen, 1980). The adults are always found near the 177 ©Societas Europaea Lepidopterologica; download unter http://www.biodiversitylibrary.org/ und www.zobodat.at food-plant, around which they fly erratically, settling either on these or low shrubs nearby. During a recent collecting trip (15th- 30th May 1987) from northern to southern Morocco, 40 localities were visited, nine of which were occupied by populations of T. theophrastus (Fig. 1). It was the only butterfly to be found abundantly. Methods & results The standarized sampling method was based on a temporal unit effort — Each locality was sampled for 30 minutes. All localities with T. theophrastus populations were of the same habitat type, consisting of open shrubland with Zizyphus bushes and some nitrophilic plants in the low vegetation strata (Peganum harmala, Salsola vermiculata and others, of the families Salsolaceae and Zygophyllaceae). This circums- tance avoids any possible habitat effect on the variation of population densities. In Table 1 the localities with T. theophrastus are summarized, giving their elevation, latitude and longitude as well as the number of individuals sampled in each of them. These data suggest an inverse correlation between the population density and altitude. Locality Altitude Longitude Latitude Number of individuals 1. Taourirt 335 2° 10' 39° 30' 19 2. Mahirija 610 3°31' 34° 5' 90 3. Meski 695 3° 46' 33° 43' 47 4. Missour 860 4° 8' 33° 15' 39 5. Amersid 1160 4° 35' 32° 47' 18 6. Tarda 1110 4° 52' 31° 20' 29 7. El Hart 1210 6° 4' 31° 3' 25 8. Tizi-n-Taddert 1360 7° 10' 30° 52' 28 9. Ouarzazate 1380 7° 30' 30° 25' 10 Table 1 . List of localities where T. theophrastus was caught with indication of the latitude, longitude, altitude as well as the number of individuals captured in each one. Fig. 2 shows the range of distribution of T. theophrastus in Morocco based upon the density data from each of the nine localities sampled and upon the data (a) taken from De Prins et al. (1984). A core of high density is centred on the plains of the north-eastern semi-arid region whose altitude varies between 600 to 800 m. A reduction in the densities is observed towards the eastern slopes of the High Atlas Mountains where the T. theophrastus distribution is interrupted. Populations of this species appear again on the 178 ©Societas Europaea Lepidopterologica; download unter http://www.biodiversitylibrary.org/ und www.zobodat.at Fig. 1 . Map of the localities visited. Those where T. theophrastus was present are numbered 1-9 (see Table 1). Fig. 2. Schematic representation of the distribution of T. theophrastus m Morocco, based upon my density data and the density data (a) of De Prins et al. (1984). 179 ©Societas Europaea Lepidopterologica; download unter http://www.biodiversitylibrary.org/ und www.zobodat.at southern High Atlas Mountains, at greater altitudes, but also at lower densities. The southern populations of Ait-Baha, Ait-Belloul, etc. (De Prins et al, 1984) are again more dense, because they are located at the lowest altitudes (about 400 m). Discussion How environmental conditions and population processes determine the abundance and distribution of a species is a central problem of ecology and biogeography. We are all aware that within their geographic ranges most species are relatively numerous in some habitats and regions, whereas they are scarce or absent in others. There is a general pattern of spatial variation in which the density is greatest near the center of the range and declines, usually gradually, towards the boundaries (see Brown, 1984 and references therein). This pattern can be explained by geographically restricted gradients of environmental change such as elevation (see i.e. Whittaker, 1960). The distribution range of T. theophrastus in Morocco is, obviously, limited by the presence of its host-plant (Zizyphus sp.). However, the different densities found among the populations can be explained by the various altitudes. 90 N.ind. 60 30 19 m.a.s.l 600 1000 1400 Fig. 3. Correlation between the altitude and the number of individuals captured. 180 ©Societas Europaea Lepidopterologica; download unter http://www.biodiversitylibrary.org/ und www.zobodat.at T. îheophrastus has, in Morocco, two cores of high density centred in the north-eastern and south-western regions. From these points, the population density decreases in all directions. The principal limiting factor seems to be the high altitudes (Fig. 3) - the presence of mountains causes a disjunct distribution (Fig. 2). This hypothesis is reinforced by the apparent absence of T. theophrastus in southern Morocco above 1000 m (see Bozano & Giacomazzo, 1988). Acknowledgements a I warmly thank D. Victor Monserrat and Dona M Luisa Diaz-Aranda, my friends and colleagues, for accompanying me on the collecting trip to Morocco. To the Culture Service of the Moroccan embassy in Spain for providing accreditation of our work in Morocco. My thanks are also due to Dona Bianca Cifrian for her help in the translation of this manuscript. Dr. J. L. Viejo kindly provided some useful, references for this paper. The comments of an anonymous reviewer greatly improved a first draft. References Balleto, E. & Larsen, T. B., 1985. On a small collection of Butterflies from Yemen. Monitore Zoologico Italiano 6 : 121-133. Benjamini, D., 1983. 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